DHCP is not supported at the moment for the WAN port in PPPoE mode you need to statically assign the address (in fact this could be added).
In my setup there is a ADSL modem which has an address 192.168.0.1. I've assigned 192.168.0.254 to my wl500g WAN port. Also, I've configured static route on the modem to route everything for 192.168.1.0/24 addresses via the 192.168.0.254 (wl500g). And this working just fine (but there is no firewall between physical wan & lan ports).
So in your case you could probably do the same thing, except you should specify the route to 192.168.1.0/24 network on all of your LAN 145... devices or just add this route to the default router routing table and it will answer with icmp error codes for correct route to anyone. But you need to establish the firewall between eth1 and br0 on the wl500g using bootCmds (but this is really tricky - wl500g tends to clear forward chain during ppp line changes, but if you've a linux experience you will notice /var/tmp/pppoe_rule[0-2] files which could be filled with the your rules via bootCmd). You could also make the simpler thing: just add the NAT between br0 and eth1 - no route changes required and you will get firewalling.
Also, you could launch dhcp client via bootCmds to get the dynamic address.
Regards,
Oleg.
